Open Paleo

Nipponosaurus

Nagao, 1936 NIP-on-o-SAWR-us

Named for Nippon (Japan), the country that controlled Sakhalin Island where the fossils were found at the time of description, combined with Greek 'sauros' meaning 'lizard'.

85.7–72.2 million years ago Santonian–Campanian, Late Cretaceous
Late Cretaceous stages

Nipponosaurus is a lambeosaurine hadrosaur from sediments of the Yezo Group, in Sinegorsk on the island of Sakhalin, which was part of Japan at the time of the species' classification. The type and only species is N. sachalinensis, known only from a single juvenile specimen discovered in 1934 and named in 1936, by Takumi Nagao, with further material of the same individual found in 1937. Since then, the taxon has been largely ignored, and its validity has been doubted, with synonymy with other Asian hadrosaurs or status as a nomen dubium being suggested. Redescriptions from 2004 and 2017, however, have supported recognition as a distinct species. Dating the only specimen has been difficult, but based on associated mollusc taxa, the species likely lived sometime in the upper Santonian or lower Campanian, around 80 million years ago.

Diagnosis

  1. Flat lateral (buccal) shelf of the dentary, anterior to the coronoid process (absent in hadrosaurids; retained from non-hadrosaurid hadrosauroids).
  2. Dorsally projecting coronoid process, its base on the dorsal surface of the dentary body and projecting nearly vertically (unlike the dorsolateral projection seen in other hadrosaurids).
  3. Lateroventral protrusion at the distal end of the manual first phalanx of digit IV.
  4. Relatively short ulna compared with the femur (ulna/femur ratio ~0.49, well below the lambeosaurine average).

Species

Nipponosaurus sachalinensis Nagao, 1936

Type species

Named for Sakhalin, the island where the holotype was found during construction of a colliery hospital in 1934.

Holotype
UHR 6590 , The Hokkaido University Museum
Material
Juvenile, more than half the skeleton: the left posterior skull (maxilla, dentary, parietal, and isolated cranial elements), cervical vertebrae, six dorsal and two sacral centra, a nearly complete caudal series, the left scapula, distal humeri and remaining forelimbs, the left ilium and ischia, and nearly complete hindlimbs.
Horizon
upper Yezo Group, Santonian–Campanian, Late Cretaceous , 85.7–72.2 million years ago
Locality
Kawakami colliery, Sakhalin, Russia Matsumoto and Obata (1979) place the horizon from the 1923 Mitsui Mining survey of the colliery: "日本竜の産地の層準は，Inoceramus schmidti 帯（K6a2）より下位すなわちInoc. orientalis 帯（K6a1）かそれ以下，つまりカンパニアン下部ないしはサントニアン上部と考えられる" (the horizon of the Nipponosaurus locality lies below the Inoceramus schmidti Zone, in the Inoc. orientalis Zone or lower, that is, lower Campanian to upper Santonian, translated).

References

  1. Nagao, T. (1936). Nipponosaurus sachalinensis: a new genus and species of trachodont dinosaur from Japanese Saghalien. Journal of the Faculty of Science, Hokkaido Imperial University, series 4, Geology and Mineralogy 3(2): 185-220. nagao1936a
  2. Matsumoto, T.; Obata, I. (1979). Evaluation of ammonites and other fossils from the Cretaceous of Japan for interregional correlation. Kaseki (Fossils) 29: 43-58.

    Obata's appendix dates the horizon lower Campanian to upper Santonian, the age Suzuki and colleagues (2004) and Takasaki and colleagues (2017) relay.

    matsumoto1979a
  3. Suzuki, D.; Weishampel, D. B.; Minoura, N. (2004). Nipponosaurus sachalinensis (Dinosauria; Ornithopoda): anatomy and systematic position within Hadrosauridae. Journal of Vertebrate Paleontology 24(1): 145-164. Informa UK Limited. doi:10.1671/A1034-11

    Comprehensive anatomical redescription of the holotype UHR 6590; confirms Nipponosaurus as a valid lambeosaurine and provides a revised diagnosis.

    suzuki2004a
  4. Takasaki, R.; Chiba, K.; Kobayashi, Y.; Currie, P. J.; Fiorillo, A. R. (2017). Reanalysis of the phylogenetic status of Nipponosaurus sachalinensis (Ornithopoda: Dinosauria) from the Late Cretaceous of Southern Sakhalin. Historical Biology 30(5): 1-18. Informa UK Limited. doi:10.1080/08912963.2017.1317766

    Osteohistology confirms a juvenile holotype; provides an ontogeny-independent amended diagnosis and recovers a basal lambeosaurine position, unlike Suzuki and colleagues 2004.

    takasaki2017a